<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>圆形盒子模型</title>
    <style>
        .circle {
            width: 100px; /* 圆的直径 */
            height: 100px; /* 圆的直径 */
            background: radial-gradient(circle at bottom right, white, black); /* 径向渐变，中心在右下角 */
            border-radius: 50%; /* 将矩形变成圆形 */
            box-shadow: 0 4px 8px rgba(0, 0, 0, 0.5); /* 添加阴影 */
        }
    </style>
</head>
<body>
    <div class="circle"></div>
</body>
</html>